Overall intensity calculation from an image

Hi,

I want to calculate the overall intensity of this image here. I have separated this red channel from an RGB flurescence image. Please guide me on how to do this.

Answer 1

[Image Analyst]

Not sure what you mean by overall intensity. You can get the red channel like this

redChannel = rgbImage(:, :, 1);
% Get sum of all pixel values:
sumOfValues = sum(redChannel(:))
% Get mean value of image intensity over all image pixels
meanIntensity = mean2(redChannel)

[Mahe Jabeen]

Hi @Image Analyst

I am doing something like this. But your approach is much easier. I am not sure why I am getting different values than yours. I converted it to gray image. Maybe it is not necessary to convert to gray image to get the sum of the intensity. Let me know what you think.

unprocessed_image=imread("G:\My Drive\codes\STB CT 30 rep1 100 pM_ hCG SDC1_ 1_c2x0-1024y0-1024.tif");

Grey_image=rgb2gray(unprocessed_image);

imshow(Grey_image);

meanIntensityValue = mean(mean(Grey_image));

[pixelCounts, grayLevels] = imhist(Grey_image);

sum_pixel=sum(pixelCounts (:,1));

[DGM]

rgb2gray() calculates luma. If all image content is in the red channel alone, then it's merely scaled by 0.299, so that's probably why you're seeing a difference. I don't see why it would be appropriate to do that, since we're not concerned with how the human eye responds to varied hues in the same image. Just extract the red channel by itself.

[Mahe Jabeen]

@DGM Thanks for the feedback. Yes, I agree.

[Image Analyst]

Summing the pixel counts from the histogram will merely count the number of pixels in the image so if you have a million pixels in your image, the sum of the histogram counts will be a million pixels. It will not give you the sum of all pixel values like I did. But again, we don't know your formula for "overall intensity" -- that's a very vague description that could be taken different ways.

[Mahe Jabeen]

Hi @Image Analyst, yes I agree with your point. My values were switched in the code I pasted and was calculating sum of intensity of all the gray pixels, not the sum of pixels.

[Image Analyst]

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